Kamaro's Mask is one of the twenty four Masks from Majora's Mask. Kamaro's Mask is received after talking to Kamaro. Kamaro can be found on one of the mushroom-shaped rocks in the snowy region of northern Termina Field.
When Link wears Kamaro's Mask, it gives him the ability to dance like Kamaro's spirit.
If Link goes to West Clock Town at night, Link finds the Rosa Sisters trying to choreograph a dance for the Carnival of Time. If Link stands in front of them and performs the dance, the siblings learn it and thank him, and in their gratitude, they give Link a Piece of Heart.